CVE-2024-57884 is a vulnerability in the Linux kernel's memory management subsystem, specifically within the virtual memory scanning (vmscan) and page reclaim logic. The issue arises in the function throttle_direct_reclaim(), which is responsible for reclaiming memory pages when the system is under memory pressure. The vulnerability is caused by an incorrect assessment of memory zone reclaimability, leading to an infinite loop in throttle_direct_reclaim(). The root cause is that the function allow_direct_reclaim(pgdat) can repeatedly return false because the node's memory zones are incorrectly deemed balanced. This happens because the zone_reclaimable_pages() function does not account for free pages (NR_FREE_PAGES) when no other reclaimable pages (inactive/active file-backed or anonymous pages) are present. In the example provided, the ZONE_DMA32 has a significant number of free pages but zero reclaimable pages, causing it to be skipped as unreclaimable. Meanwhile, another zone, ZONE_NORMAL, remains under memory pressure but the overall node is considered balanced due to the free pages in ZONE_DMA32. This misclassification prevents the increment of kswapd_failures, a counter used to indicate memory reclaim failures, and causes the system to incorrectly believe memory pressure is resolved. Consequently, throttle_direct_reclaim() loops infinitely, as allow_direct_reclaim() never returns true, leading to a kernel hang or system freeze. The patch for this vulnerability modifies zone_reclaimable_pages() to include free pages in its reclaimable pages calculation when no other reclaimable pages are available. This ensures zones with free pages are not mistakenly skipped, allowing proper node balancing and preventing infinite loops in memory reclaim operations. The vulnerability affects Linux kernel versions identified by the commit hash 5a1c84b404a7176b8b36e2a0041b6f0adb3151a3 and similar. This vulnerability does not require user interaction or authentication to trigger but depends on specific memory pressure conditions and system configurations, such as the absence of swap space. It can cause system hangs, impacting availability severely.

For European organizations, the impact of CVE-2024-57884 can be significant, especially for those relying heavily on Linux-based infrastructure, including servers, cloud environments, and embedded systems. The vulnerability can cause kernel hangs and system freezes due to infinite loops in memory reclaim functions, leading to denial of service (DoS). This can disrupt critical business operations, affect service availability, and cause downtime. Organizations running Linux kernels with the affected versions and configurations lacking swap space are particularly vulnerable. This includes data centers, cloud service providers, and enterprises using Linux for high-performance computing or container orchestration platforms like Kubernetes. The inability to reclaim memory properly under pressure can degrade system performance and reliability. Given the widespread use of Linux in European public sector institutions, financial services, telecommunications, and manufacturing, the vulnerability poses a risk to critical infrastructure and services. Prolonged system hangs could lead to operational disruptions, financial losses, and reputational damage. Additionally, recovery from such hangs may require manual intervention or system reboots, increasing operational overhead.

1. Apply the official Linux kernel patch that addresses CVE-2024-57884 as soon as it becomes available. Monitor Linux kernel mailing lists and vendor advisories for updates. 2. Upgrade to a Linux kernel version that includes the fix for this vulnerability. If immediate upgrade is not feasible, consider backporting the patch if supported by your distribution. 3. Configure systems to use swap space where possible. The vulnerability is exacerbated in systems without swap, so enabling swap can reduce the likelihood of triggering the infinite loop. 4. Monitor system memory usage and kernel logs for signs of memory pressure or reclaim failures. Implement alerting for unusual kernel scheduling delays or system responsiveness issues. 5. For critical systems, implement redundancy and failover mechanisms to minimize impact from potential kernel hangs. 6. Test kernel updates in staging environments to ensure stability and compatibility before production deployment. 7. Engage with Linux distribution vendors for security advisories and recommended mitigation steps tailored to your environment.